It is known in orthopaedics to measure the mobility and the grip strength of the hand as a means of assessing injury or disease and recovery from them. One example of this is in assessing stiffness of the hand following fracture of the metacarpal bones. Measurement of the absolute value of grip strength gives a reasonable assessment of the progress of recovery; known grip meters used for this purpose are marketed by MIE Medical Research and Jamar Inc.
This method of assessment is, however, dependent on the subject making a genuine effort to exert maximum grip during the test. It is believed that some subjects deliberately attempt to conceal the degree of recovery by applying less than maximum grip. This may happen for example where there are considerations of insurance claims or industrial injury compensation.
It has previously been proposed to assess grip sincerity from force measurement; see
1. "Simple method to determine sincerity of effort during a maximal isometric test of grip strength", J. C. Gilbert et al., Amer. J. of Physical Medicine, 1983, pp 135-143.
2. "Assessing sincerity of effort in maximal grip strength tests", G. A. Smith et al., Amer. J. of Physical Medicine and Rehabilitation, 1989, pp 73-80.
It is believed, however, that these prior proposals do not provide results useful in practical evaluation. One reason is that they base the evaluation on a comparison of peak strength to average strength, which is not a reliable indicator. Another is that they assume a genuine grip to have a substantially constant force over a period of some seconds, whereas in fact the strength of a genuine grip decays relatively quickly over timescales of even a few seconds due to fatigue.